1. Field of the Invention
The present invention relates to a device for gutter selection in a transmission, in particular, in AMT systems (automatic manual transmission) as well as a method for the gutter selection in a transmission.
2. Description of the Related Art
In so-called automatic manual transmissions (AMT) the gears of the transmission are shifted by means of an electro-hydraulic actuator. In this connection, the actuator for a transmission with an xe2x80x9cHxe2x80x9d shifting pattern is configured of several pistons and corresponding mechanisms in order to carry out the gear shifting movement and/or gutter movement.
Such an actuator is known, for example, from DE 199 31 973 A1. In this connection, a complexly configured unit comprised of actuating devices, sensors, and valve devices is proposed in order to move a selector finger in a gutter of the transmission.
In FIG. 5, a different gutter selection actuator is illustrated. As shown in FIG. 5, the actuator comprises six piston elements 31, 32, 33, 34, 35, and 36 in order to position the selector shaft 37 in one of the transmission gutters N1, N2, N3 or N4. The position of the piston units 31 through 36 is determined by control of two switching valves SV1 and SV2. Such an actuator requires a complex mechanical configuration and has a plurality of components. This results in an increased manufacturing expenditure and a highly branched hydraulic line system. Moreover, a control must be provided in order to control the two switching valves SV1 and SV2.
It is therefore an object of the present invention to provide a device as well as a method for gutter selection which enables a safe and reliable gutter selection while providing a simple configuration and a simple, inexpensive manufacture.
This object is solved by an actuator for gutter selection comprising a selector shaft with a selector finger and a gutter selection device which is movable back and forth along an axis in order to assume a first position and a second position, wherein the selector finger of the selector shaft can be moved into engagement and out of engagement with the gutter selection device and wherein the position of the gutter selection device can be determined by means of precisely one valve device. The object is further solved by a method for gutter selection comprising the steps of positioning the gutter selection device, movable back and forth along an axis, in a first position depending on the desired next gutter selection; connecting a selector shaft with the gutter selection device; moving the gutter selection device with the selector shaft into a second position so that the selector shaft is positioned in a neighboring gutter; and disengaging the selector shaft from the gutter selection device in order to shift a gear, wherein the movement of the gutter selection device from the first position into the second position is carried out by means of precisely one valve device. Advantageous embodiments are the subject matter of the dependent claims, respectively.
According to the invention, an actuator for gutter selection of a gear positioning device for an automatic manual transmission is thus proposed which comprises a selector shaft with a selector finger and a gutter selection device. The gutter selection device is movable back and forth along an axis and, in this connection, assumes a first position and a second position. In this way, the gutter selection device can assume only precisely two positions. In this connection, the selector finger of the selector shaft can be engaged with and disengaged from the gutter selection device. The position of the gutter selection device is determined in this connection by precisely one valve device.
Accordingly, the gutter selection actuator according to the invention is of a very simple configuration because the selection of the gutter can be realized with a single valve device. In this connection, only one gutter selection device is required which is controlled by the only valve and which must perform only an axial reciprocating movement in order to perform the gutter selection. Accordingly, the actuator according to the invention for gutter selection only has a minimal number of components so that a minimal manufacturing expenditure and a minimal assembly expenditure result. Accordingly, the actuator according to the invention for gutter selection can be manufactured significantly less expensively in comparison to previously employed gutter selection actuators. Due to the minimal number of components the reliability of the system can also be improved.
Moreover, since only one valve device is employed, savings in regard to electronic compounds and in regard to a wiring harness result also, since only one valve device must be controlled. Moreover, the system according to the invention does not require a sensor because the position of the gutter selection device is determined simply by the position of the valve device. Accordingly, no redundancy sensor is necessarily required which could maintain an emergency operation when the sensor fails. Since the gutter selection device and the selector finger are completely out of engagement after gutter selection, it is also ensured that, when the gear is engaged, no forces are exerted by the gutter actuator onto the transmission. This increases the service life of the transmission.
Preferably, the gutter selection device is embodied as a piston which is loaded with a pressure medium. In this connection, the piston can be guided simply in a housing and can have a simple configuration. The control of the piston is realized in this connection via the valve device which supplies the pressure medium to the piston. The pressure medium is preferably a hydraulic liquid.
It is especially preferred to embody the piston as a double-action piston. In this connection, the valve device controls the piston on a certain piston end as a function of the position of the piston. Preferably, the piston has two piston surfaces with differently sized surface areas. This enables that the piston can be loaded on both surfaces with a control pressure of the same magnitude and that the piston is always in a defined position.
Advantageously, the gutter selection device is provided with cutouts for engagement by the selector finger. In this way, a positive-locking connection between the gutter selection device and the selector finger can be provided.
Preferably, the cutouts are arranged such on the gutter selection device that the selector finger can engage the gutter selection device by means of a pivot movement. This enables a simple and safe course of movement for the selector finger for engaging and releasing the gutter selection device.
Preferably, the selector finger can pivot in two directions in and out of the gutter selection device. In this way, the individual gears can be selected by a direct pivot movement out of the gutter selection device. This enables an especially compact configuration.
Preferably, the number of cutouts provided in the gutter selection device is smaller by one compared to the number of the gutters of the transmission. This means that when the transmission has, for example, four gutters, the gutter selection device has three cutouts. In this way, the constructive size of the gutter selection device can be kept small.
Preferably, the stroke of the piston (gutter selection device) matches the spacing of two neighboring gutters of the transmission. This ensures that the selector finger or the selector shaft are moved precisely by one next gutter.
In order to provide an additional safety device in regard to the position of the gutter selection device, a sensor is preferably provided in order to determine the position of the gutter selection device. As has been explained before, the position of the gutter selection device can also be determined according to the invention simply by the position of the valve device.
In order to enable for a shifting process a skipping of gutters, the selector finger can be moved into an intermediate position in which it is out of engagement with the gutter selection device as well as with the transmission. This makes it possible that the gutter selection device can be returned into its other position (initial position), and the selector finger can subsequently engage the gutter selection device and, by movement of the gutter selection device, can be moved into the next gutter. Accordingly, during the shifting action a gutter can be skipped without this requiring the shifting of a gear in the skipped gutter.
Preferably, the valve device is a 3/2 directional control valve. In this way, it can be manufactured simply and inexpensively and provides a simple and reliable control action.
According to the method of the invention for gutter selection in a gear positioning device for an automatic manual transmission, in a first step a gutter selection device, movable along an axis in a reciprocating fashion, is fixed in position. In this connection, the gutter selection device can assume only two positions. Possibly, a positioning of the gutter selection device is carried out only when the momentary position does not correspond to the desired initial position. Positioning is realized depending on the desired next gutter selection (i.e., depending on the direction in which the next gutter, in which the desired gear is located, is positioned). In a second step, a selector shaft is connected by a selector finger with the gutter selection device, i.e., is engaged. In a third step, the gutter selection device with the selector shaft is moved into a second position (target position). In this way, the selector shaft is positioned in a gutter neighboring the original initial gutter. In a fourth step, a selector shaft is disengaged from the gutter selection device. For this purpose, the selector finger is moved out of the gutter selection device and the desired gear is shifted. In this connection, the movement of the gutter selection device is carried out only by means of precisely one valve device. With the method according to the invention, it is thus possible, in principle, to embody a gutter actuator in which a gutter is selected by using only two movement directions. In this connection, the movement directions are positioned on one axis and the gutter selection device is moved on the axis in opposite directions, respectively. In this way, the process of gutter selection can be significantly simplified.
In order to enable a safe movement between gutter selection device and selector finger, the selector shaft is advantageously movable into engagement and out of engagement with the gutter selection device by a pivot movement.
Preferably, the gutter selection device is embodied as a piston having two piston surfaces and actuatable on both ends. This enables a particularly simple control of the gutter selection device. It is particularly preferred to load the two piston surfaces with the same control pressure, wherein the two piston surfaces are of different size. This enables a particularly simple control of the device according to the invention for gutter selection.